Polycom SIP 2.2.0 ユーザーズマニュアル

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Administrator’s Guide SoundPoint IP / SoundStation IP 
4 - 36
Phone Configuration
The phones at the customer site are configured as follows:
• Server 1 (the primary server) will be configured with the address of the 
service provider call server. The IP address of the server(s) to be used will 
be provided by the DNS server. For example:
reg.1.server.1.address="voipserver.serviceprovider.com"
• Server 2 (the fallback server) will be configured to the address of the 
router/gateway that provides the fallback telephony support and is 
on-site. For example:
reg.1.server.2.address=172.23.0.1
Warning
If DNS is used to resolve the address for Servers, the DNS server is unavailable, 
and the TTL for the DNS records has expired, the phone will attempt to contact the 
DNS server to resolve the address of all servers in its list before initiating a call. 
These attempts will timeout, but the timeout mechanism can cause long delays (for 
example, two minutes) before the phone call proceeds “using the working server”. 
To mitigate this issue, long TTLs should be used. It is strongly recommended that 
an on-site DNS server is deployed as part of the redundancy solution.
 
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PSTN Gateway
Internet
PSTN
Hosted VoIP Service 
Provider
VoIP SMB Customer 
Premise
DNS Server
Call Server 1A
Call Server 1B
SIP Capable Router
Server2
Note
It is possible to configure the phone for more than two servers per registration, but 
you need to exercise caution when doing this to ensure that the phone and network 
load generated by registration refresh of multiple registrations do not become 
excessive. This would be of particularly concern if a phone had multiple 
registrations with multiple servers per registration and it is expected that some of 
these servers will be unavailable.